Three bombs have exploded in the capital of Burma, killing at least 11 people and wounding scores of others. State television blamed several ethnic rebel groups for the attacks, including the Karen National Union and the Shan State Army.

The blasts occurred Saturday afternoon in Rangoon at two busy shopping centers and a convention center, where Thailand was hosting a trade fair.

No one has claimed responsibility, but the Burmese government has blamed similar attacks on what it calls, "destructive elements," a reference to civilian opposition and ethnic rebel groups. But the coordinator of the ALTSEAN pro-democracy advocacy group, Debbie Stothard, says that opponents of the regime in the past have linked such attacks to the military government.

Burma's military junta faces opposition from ethnic rebel groups and civilian pro-democracy parties. But Ms. Stothard says these groups are unlikely to have been behind the attacks because of the military's tight control over security.

"I seriously doubt that any of the opposition groups would be involved in such an activity, simply because Rangoon is tied up so tightly by the military regime. It is highly unlikely that any underground groups would have access to that kind of equipment required for bombs," she said.

Burmese politics have been unsettled since a power struggle within the military leadership last year lead to the dismissal of then-Prime Minister Khin Nyunt and the dissolution of the powerful military intelligence organization, which he lead.

Independent observers note that, during the shake-up, extensive business interests of the former prime minister's associates were taken over, and hundreds of senior officers were detained.

In February, the government reconvened a national convention to draft a constitution leading to elections, part of a road map toward democracy.

But major opposition parties and ethnic rebels did not attend the convention, leading pro-democracy groups and western governments to criticize it as maneuver by the military to legitimize its power.

Saturday's explosions occurred as Asian and European foreign ministers, meeting in Japan, urged the Burmese government to speed up political reforms and free political detainees.